Thermal diffusivity measurement of uranium-thorium-zirconium hydride

The uranium-thorium mixed zirconium hydrides of UTh₄Zr₁₀H_x (x = 20, 24, 27) have been successfully fabricated without large crack by means of a Sieverts apparatus. The scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses show that UTh₄Zr₁₀H_x consist of α-U, ThZr₂H_x, and (δ, ε)-ZrH_x. The thermal diffusivity measurements of UTh₄Zr₁₀H_x have been performed over the temperature ranges to around 773 K by means of a laser-flash method. It is shown that as the hydrogen concentration increases, the thermal diffusivity increases under 600 K and decreases above 600 K. The temperature dependence of the thermal diffusivity can be expressed with the simple equation as functions of composition and temperature. The thermal conductivity of the UTh₄Zr₁₀ hydrides has been also evaluated from the measured data of the thermal diffusivity and the density and the estimated data of the specific heat and found to be close to those of U-carbide or -nitride at around 773 K.